1. Field of the Invention
The invention relates to a television receiver for receiving a plurality of television channels, at least some of said television channels carrying a data signal representing pages of information to be displayed, said data signal being multiplexed with the television program transmitted in said channel.
2. Description of the Related Art
The transmission of data multiplexed with a television signal is well known. An example is the teletext standard in which data representing pages of information to be displayed, is sent in the vertical blanking interval of a standard analog television picture signal. In addition, with the introduction of MPEG-encoded digital television transmissions, there is provision for data signals to be multiplexed in the digital data streams. The data represents pages of information, and, in this context, a page refers to a quantity of data which is displayed at one time on a television display. Thus, normally, one page will be displayed at a time, although it is possible to have a split screen and display a number of pages simultaneously.
It has been found that typical viewers will select a small sub-set of the pages which are transmitted as being of interest to them and will access these pages much more frequently than others. As a result, television receivers have been produced which store the numbers of those pages which the user habitually accesses. When the receiver is switched on, it is arranged to automatically search for those particular pages in the transmission cycle of the data associated with the channel which is selected for viewing, so that they are acquired and stored in memory. Thus, when the viewer wants to access these favorite pages, they are already stored in memory so that it is not necessary to wait for them to occur in the transmission cycle. One of the major criticisms of the teletext system is the time required to access a particular selected page. This depends on when, in the cycle of transmission, a page is requested. The delay can be particularly significant when sub-pages or revolving pages are used, particularly if there are a large number of them.
It is an object of the invention to enable the speed of acquisition of the favorite pages of a viewer to be increased.
The invention provides a television receiver for receiving a plurality of television channels, at least some of said television channels carrying a data signal representing pages of information to be displayed, said data signal being multiplexed with the television program transmitted in said channel, said receiver comprising means for selecting each of the received channels, means for storing addresses of favorite pages of data associated with at least some of said channels, means for causing the receiver to automatically select each of the channels having associated therewith stored addresses of favorite pages in turn, to acquire the data representing the favorite pages for each channel, and to store the data, and means for selecting one or more of the stored favorite pages.
With prior art television receivers, the favorite pages which are stored are those which are associated with the channel which is currently being received. There is no means of acquiring the favorite pages associated with other television channels as only those data signals associated with the channel being viewed are presented to the acquisition circuits. Consequently, when the viewer changes channels there is a delay before the favorite pages associated with the new channel are acquired. At the same time, the favorite pages associated with the channel which was previously being watched are lost.
A television receiver in accordance with the present invention acquires and stores the data representing the favorite pages for each channel. These pages are stored in a dedicated portion of memory which is allocated for favorite pages of each of the channels. Thus, on changing channels, the data is not overwritten by new data received from teletext or other data transmissions associated with the newly received channel.
The television receiver may comprise means for causing the receiver to scan all the channels having associated therewith favorite pages to acquire and store the favorite pages each time the receiver is switched on.
By this means, the capture of the favorite pages for each channel is ensured in the fastest possible time and, frequently, the viewer will not be particularly interested in the program being transmitted when the receiver is first switched on. Thus, the viewer will not object to not being able to watch a program on a particular channel during the time taken to scan the channels and enter the favorite pages into the memory.
Alternatively, or in addition, the television receiver may comprise user operated means for instructing the receiver to scan those channels having associated favorite pages to acquire and store said favorite pages at a time determined by the user.
By enabling the user to initiate the scanning of the channels, this operation can be carried out at a time convenient to the user. For example, if the user switches on the television receiver at a time when the program being broadcast is one which is of interest to the viewer, then the interruption of the program caused by the scanning of the various channels could be annoying. If, however, the user is provided with means to choose the time at which the scanning takes place, this can be done at a time when the program being broadcast is not of interest. The receiver may be arranged, in a default state, to scan all the channels when it is switched on, but there may be an override instruction operable by the user to prevent the scanning from occurring if the user is interested in a particular program being transmitted at that time. Thus, for example, two buttons may be provided on a remote control unit, one of which is used to disable the automatic scanning when the receiver is switched on, and the other of which is used to initiate scanning at a time convenient for the user. Alternatively, a single button could be used whose function is to change the mode from scanning to non-scanning and vice versa. This is similar to the arrangement on many current remote control units for switching between text and picture where the same button is used to change in both directions.
The television receiver may comprise means for causing the receiver to select each of the channels for a period at least as long as the cycle time of the transmitted data.
Teletext data is transmitted in serial form, one page succeeding another. Consequently, it takes a finite time for any given page to appear in the transmission cycle. The transmission of teletext data is such that the pages reappear at regular intervals dependent on the number of pages which are being transmitted by the broadcaster. This cycle time is normally of the order of 30 seconds, that is, any given page will reappear in the transmission at approximately 30 second intervals. Thus, if the receiver selects each of the channels for a period somewhat in excess of that 30 seconds, the favorite pages should all be acquired during that time.
In an alternative embodiment, the television receiver comprises detection means for detecting when all of the favorite pages associated with the selected channel have been acquired and stored, and means for selecting the next channel in response to the output of the detection means.
This will ensure that all of the favorite pages are actually acquired and stored before the receiver moves on to the next channel. This has the advantage that if, for example, interference causes one of the favorite pages to be corrupted and, hence, not be acquired, then the receiver will stay tuned to the selected channel until the page is re-transmitted. In addition, this will enable rolling pages to be captured, if, for example, one of the favorite pages has a number of rolling pages associated, then the total cycle time will be increased, but by moving on to the next channel only when it has been detected that all the pages in the favorite pages list have been acquired, it is possible to ensure that all the pages that the viewer wishes to have stored have been stored during this scanning process.
The television receiver may comprise means for detecting which pages of data are currently being transmitted, and said detection means may be arranged to detect when all transmitted favorite pages have been acquired and stored.
Broadcasters do not always transmit every page of each magazine of teletext data. This will depend on whether the particular topic for that page currently has any information. An example is that those pages which relate to results from an event shortly to take place may not be transmitted until either the event starts or a final result is available. In the version of teletext known as TOP, a special page known as Table Of Pages is transmitted which lists all the pages which are currently in the transmission cycle. By comparing this list with the favorite page numbers, it can be established which favorite pages are currently being transmitted, and, in this case, the detection means is arranged to produce an output indicating the acquisition and storage of the favorite pages once all the currently transmitted favorite pages have been acquired and stored. For teletext transmissions of other standards where a list of the pages currently in the transmission cycle is not transmitted, teletext decoders are known which monitor the transmission to determine which pages are currently be transmitted, and keep a list of such pages. This list can be used in conjunction with the List of Favorite Pages to determine when all the favorite pages currently being transmitted have been acquired and stored.
An alternative to this arrangement which will prevent the scanning from being locked onto a particular channel if not all the favorite pages are being transmitted, is to combine the detection means with an overall time limit so that if all the favorite pages are not acquired after a time which corresponds to a plurality of transmission cycles, it is assumed that those pages not acquired are not being currently transmitted. The actual number of transmission cycles to which the time limit corresponds should be chosen to be as few as possible consistent with ensuring that those favorite pages which are being transmitted will be acquired and stored. This number will also depend on whether it is desired to capture any sub-pages associated with the favorite pages, and the number of such sub-pages which can be catered for.
The television receiver may further comprise means for selecting, for display, favorite pages associated with channels other than that to which the receiver is currently tuned, for reception.
It may be that a viewer would like to access teletext or other data pages which are not associated with the particular program currently being watched. Thus, for example, a viewer may wish to view the teletext pages relating to a particular news item or sports item on a different channel from the one which is currently being displayed. In order to do that, in prior art receivers, the viewer had to change channels and wait for the teletext pages to be acquired, and was unable to continue watching the program transmitted on the original channel. It will be realized, of course, that, standard television receivers which are equipped for receiving teletext and other data, normally have a display mode called xe2x80x9cmixed modexe2x80x9d where the text is superimposed on the picture. Thus, the viewer can continue viewing the program while reading teletext text which is associated with either the current channel or with other channels. Thus, by providing storage where the teletext pages are stored in dedicated locations for each channel, these pages may be accessed regardless of whether that channel is currently being received. It will be apparent, of course, that any teletext data which is stored and which is associated with channels other than that being currently received will not be updated. In most cases, however, this is not of great significance as the teletext data transmitted by the broadcaster is not normally frequently updated, although there are particular pages where relatively continuous updating does occur. Since many of the pages are only updated daily, or perhaps two or three times a day, the fact that the teletext data associated with other channels are not being updated is not a major disadvantage.
On completion of the acquisition of the favorite pages, the television receiver may revert to selecting the previously received channel. Thus, on switch on, it may be arranged that after the channels have been scanned and the favorite pages acquired, the television receiver selects the channel that was being viewed immediately before it was last switched off. In the alternative situation, where the viewer is instructing the receiver to scan the channels, then the receiver, after it has acquired the favorite pages, will revert to selecting the channel which was being viewed at the time the viewer requested the acquisition of the favorite pages.
The invention further provides a television receiver as set forth above having two channel selectors, wherein the first channel selector is arranged to select a channel for viewing and/or acquisition of the data signal associated with that channel, and the second channel selector is arranged to select, in turn, each channel for which favorite pages of data exist, and to acquire those favorite pages being transmitted in each of those channels.
By using one channel selector (or tuner) for selecting the channel for viewing and a further channel selector (or tuner) for scanning the other channels to acquire the favorite pages of data, the disadvantage that when the channel scanning is initiated at the time of switch on this may prevent a viewer from watching a program which is being transmitted on one channel, is overcome, since there is no requirement that the acquisition of the data signal should cause the channel being viewed to change. In this embodiment, the acquisition of the favorite pages of data takes place in the background and is transparent to the viewer who merely sees the result of obtaining the favorite pages for the other channels by having faster access to the favorite pages of the other channels when called up using a remote control unit, but is not aware of the receiver undertaking the process.
The television receiver may comprise means for causing the second channel selector to continuously cycle round those channels having favorite pages of data associated with them to enable the data stored to be updated.
While much of the teletext data which is transmitted by broadcasters is not updated frequently, some pages are frequently updated. An example is a page containing current scores in sports matches. These pages are not necessarily transmitted with all channels, and if a viewer wishes to have this updating while watching a channel that does not have such data associated with it, then the continuous cycling of the second channel selector enables those pages to be updated, even though a program on a different channel is being viewed.
The television receiver may comprise means for preventing the second channel selector from selecting the channel which is presently selected by the first channel selector. If the receiver includes two data acquisition channels, then the first channel selector may feed its output to the first data acquisition channel while the second channel selector feeds its output to a second data acquisition circuit. In this way, the channel which is currently being viewed may have its data pages constantly updated without having to wait for the channel selector to scan round to that particular channel. This is of increasing importance as the number of channels increase, since with typical cycle times, it will take approximately thirty seconds to scan each channel and with ten channels, this would mean that the pages could be updated only once every five minutes.
The television receiver may comprise means for causing the second selector to stop cycling round those channels having favorite pages of data associated with them.
Television receivers are known which have more than one channel selector or tuner. The second channel selector may be used to select a channel for display as a Picture-In-Picture (PIP) or for selecting a channel for recording; particularly, when the television receiver is combined with a video recorder. In these circumstances, the second channel selector may be used not only for displaying a PIP or for selecting a channel for recording, but while the PIP or recording function is not selected, may also be used as the second selector which cycles round the other channels having favorite pages associated with them. Consequently, in this case, no additional channel selector or tuner is required. The control means is merely required to cause the output of the second channel selector to be directed to the PIP display, to the recorder, or to the data store.
The present invention relates to television receivers for receiving both analog television signals having a teletext transmission associated therewith, and digital television data streams which have multiplexed therewith a data signal representing pages of information in a manner similar to the teletext data in analog television. Thus, the channel selector may be a standard television tuner for analog television signals or may be a demultiplexer for selecting one of the channels from a digital data stream containing a number of channels. In addition, where a number of separate digital multiplexes are transmitted, the channel selector may comprise a combination of tuner and demultiplexer circuits.